Antifreeze corrosion inhibitor



atente pr. ii,

poration or New York L Bayw, l- :3?

hide and Garbon Chemicals florporation, a cor- No Bra. Application August e, 1937,

The invention relates to non-corrosive antifreeze liquids of the type commonly. used as a cooling fluid in internal combustion engines and employing an alcohol as the freezing point depressant. It is particularly concerned with corrosion inhibitors for such liquids adapted specifically for protection of aluminum when in contact therewith.

The use of monohydric and polyhydric alcohols as freezing point depressants in cooling fluids has been quite generally adopted, and includes alcohols such as methanol, ethanol, propanol, ethylene glycol, other glycols andpolyglycols, and glycerol. In dilution with water as an anti-freeze, and under conditions of use com monly encountered in automobile cooling systems, there is usually induced in solutions of these alcohols a corrosive action toward metals, although the alcohols themselves in pure form are not considered corrosive. The necessity for protecting metals in contact with alcohol antifreeze solutions has, therefore, been recognized, and for this purpose a great many materials, in the nature of additive inhibitor agents have heretofore been proposed in the art. Dimculty has been encountered, however, in obtaining in this manner satisfactory and effective protection for all metals of the usual automobile cooling system, which commonly contains the metals, iron, copper, brass, solder and aluminum; in astructure necessitating contact of these with the cooling fluid. Inhibitors comprising a mixture of a number of separate compounds have been used in an effort to provide complete protection for all metals, but prevention of corrosive conditions toward aluminum, severe enough to effect pitting of the metal, has been especially difilcult to control.

The present invention is concerned specifically with aluminum protection, and it is an object to provide an inhibitor agent which will maintain non-corrosive conditions toward aluminum in a cooling'fluid in contact therewith. particularly a fluid containing an alcohol as a freezing point depressant.

I have found that soluble nitrate salts afi'ord excellent corrosion protection for aluminum in aqueous alcohol solutions, and such salts are particularly efiective in the prevention of aluminum pitting which is quite often encountered in cooling systems where copper and aluminum are used in quite close contact. A maximum of about 1.0% of the nitrate by weight of the alcohol is preferred, and in quantities as small as 0.01% by weight the salt will exert a noticeable protective action. Since larger amounts may adversely af-' have given excellent results, and a concentration of about 0.2% sodium nitrate will protect aluminum under all conditions normally encountered in use of an alcohol cooling fluid.

The nitrate salt may be used in the presence of. and in mixture with, other known inhibitors which may be added as protection for the other metals of a cooling system, and even in formulae intended to include an aluminum inhibito it will be found that further small additions of a soluble nitrate will greatly improve the inhibiting action of the mixture and prolong its useiul life. In all of the common anti-freeze alcohols, and in the various aqueous dilutions thereof usually. employed in a cooling fluid, the nitrate will maintain its inhibiting function, and the most suitable proportions can be readily determined for. any particular conditions of use.

' Many modifications in this disclosure will be evident to those skilled in the art, particularly with respect to formulae including other inhibitor materials in conjunction with a soluble nitrate. It will be understood that aluminum metal as referred to herein includes the metal in pure form as well as alloys thereof in which aluminum predominates, and the nitrate inhibitor is effective in protecting any such metals. The invention should not be limited other than as defined by the appended claims.

Iclaim:

1. A non-corrosive anti-freezellquid comprising an alcohol and an inhibitor containing as the essential corrosion preventive for aluminum a soluble nitrate salt in an amount of about 0.01% to 1.0 by weight of the alcohol.

2. A non-corrosive anti-freeze liquid comprising an alcohol and an inhibitor containing as the essential corrosion preventive for aluminum an alkali metal nitrate in an amount of about 0.01% to 1.0% by weight of the alcohol.

3. A non-corrosive anti-freeze liquid comprising an alcohol and an inhibitor containing about 0.01% to 1.00% by weight of. the alcohol 01' sodium nitrate as the essential corrosion preventive for aluminum.

4. A non-corrosive anti-freeze liquid: comprising a glycol and an inhibitor containing about 0.01% to 1.00% by weight of the glycol of sodium nitrate as the essential corrosion preventive for aluminum.

5. A non-corrosive anti-freeze liquid comprising ethylene glycol and an inhibitor containing about 0.01% to 1.00% by weight of the ethylene glycol of sodium nitrate as the essential corrosion preventive for aluminum.

6. A non-corrosive anti-freeze liquid comprising ethylene glycol and an inhibitor containing about 0.2% by weight of the ethylene glycol of sodium nitrate as the essential corrosion preventive for aluminum. I

7. Method of inhibiting corrosion of aluminum by an alcohol containing cooling fluid in contact therewith which comprises contacting said fluid with aluminum in the presence of aboutalkali metal nitrate.

tact therewith, which comprises contacting said fluid with aluminum in the presence oi about 0.01% to 1.0% by weight of the alcohol of an 9. Method of inhibiting corrosion of aluminum by an alcohol containing cooling fluid in contact therewith, which comprises contacting said fluid with aluminum in the presence. of about 0.01% to 1.0% by weight of the alcohol of sodium nitrate,

10. In a cooling system employing aluminum in contact with an alcohol containing cooling fluid means for preventingaluminum corrosion comprising sodium nitrate dissolved in said fluid in an amount not substantially greater than 1.0% by weight of the alcohol.

ALFRED L. BAYES. 

